Vehicle exterior environment recognition apparatus

ABSTRACT

A vehicle exterior environment recognition apparatus includes a computer and an illumination mechanism. The computer serves as a preceding vehicle extractor that extracts a tail lamp of a preceding vehicle, a preceding vehicle recognizer that recognizes the preceding vehicle on a basis of the extracted tail lamp, and a light-distribution controller that determines a light distribution of a headlamp. The illumination mechanism switches between a low beam and a high beam on a basis of instruction issued by the light-distribution controller. The preceding vehicle extractor acquires instruction information related to the instruction on the determination issued by the light-distribution controller and result information related to a result of beam application performed by the illumination mechanism, and extracts, by a threshold corresponding to the low beam, the tail lamp for a region in which either one of the instruction information and the result information indicates application of the low beam.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from Japanese Patent ApplicationNo. 2015-229928 filed on Nov. 25, 2015, the entire contents of which arehereby incorporated by reference.

BACKGROUND

The technology relates to a vehicle exterior environment recognitionapparatus that performs a light-distribution control of headlamps, onthe basis of an environment outside a vehicle, i.e., a vehicle exteriorenvironment.

A technique has been known in which a three-dimensional object, such asa preceding vehicle located ahead of an own vehicle, is detected toperform a control that avoids collision with the preceding vehicle(i.e., a collision avoidance control) or to perform a control that keepsan inter-vehicular distance between the own vehicle and the precedingvehicle to a safe distance (i.e., a cruise control). For example,reference is made to Japanese Patent No. 3349060.

Further, with the increasing adoption of an auto light function for safetraveling at night, a technique has been developed in which brightnessof a surrounding environment is determined on the basis of exposureinformation obtained from a monitor sensor and a result of thedetermination is utilized for the auto light function. For example,reference is made to Japanese Unexamined Patent Application Publication(JP-A) No. H11-187390. The auto light function turns on headlampsautomatically when brightness outside the vehicle becomes insufficient.A technique has been also developed in which a light-distributioncontrol of the headlamps is performed on the basis of tail lamps of thepreceding vehicle, as disclosed in JP-A No. 2013-209035.

SUMMARY

Upon performing a light-distribution control of headlamps, it isdesirable that tail lamps of a preceding vehicle be identifiedaccurately to prevent the preceding vehicle from being irradiated withhigh beams. What is therefore desired is further improvement inidentification accuracy.

It is desirable to provide a vehicle exterior environment recognitionapparatus that increases identification accuracy of a tail lamp of apreceding vehicle.

An aspect of the technology provides a vehicle exterior environmentrecognition apparatus that include: a preceding vehicle extractor thatextracts a tail lamp of a preceding vehicle from an image; a precedingvehicle recognizer that recognizes the preceding vehicle on a basis ofthe tail lamp extracted by the preceding vehicle extractor; and alight-distribution controller that determines a light distribution of aheadlamp of an own vehicle on a basis of a result of the recognitionperformed by the preceding vehicle recognizer, and a illuminationmechanism switches between a low beam and a high beam of the headlamp ona basis of an instruction issued by the light-distribution controller.The preceding vehicle extractor acquires instruction information relatedto the instruction on the determination on the light distribution issuedby the light-distribution controller and result information related to aresult of beam application performed by the illumination mechanism, andextracts, by a threshold that corresponds to the low beam, the tail lampfor a region in which either one of the instruction information and theresult information indicates application of the low beam.

Another aspect of the technology provides a vehicle exterior environmentrecognition apparatus that includes circuitry and an illuminationmechanism. The circuitry extracts a tail lamp of a preceding vehiclefrom an image, recognizes the preceding vehicle on a basis of the taillamp extracted from the image, and determines a light distribution of aheadlamp of an own vehicle on a basis of a result of the recognition ofthe preceding vehicle. The illumination mechanism switches between a lowbeam and a high beam of the headlamp on a basis of an instruction thatis issued on a basis of the determination on the light distribution. Thecircuitry acquires instruction information related to the instruction onthe determination on the light distribution issued on the basis of thedetermination and result information related to a result of beamapplication performed by the illumination mechanism, and extracts, by athreshold that corresponds to the low beam, the tail lamp for a regionin which either one of the instruction information and the resultinformation indicates application of the low beam.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a relationship of connection in avehicle exterior environment recognition system.

FIG. 2 is a functional block diagram illustrating schematic functions ofa vehicle exterior environment recognition apparatus.

FIG. 3 is a flowchart illustrating an example of a flow of a vehicleexterior environment recognition process.

FIG. 4A and FIG. 4B respectively describe a luminance image and adistance image.

FIGS. 5A, 5B, 5C and 5D describe an example of a determination processto be performed by a necessity determiner.

FIG. 6 describes detection ranges.

FIG. 7A and FIG. 7B describe luminance images that are different fromeach other in exposure time.

FIG. 8 is an explanatory diagram for describing a relationship betweentail lamps and a red reflector.

FIGS. 9A and 9B are another explanatory diagram for describing therelationship between the tail lamps and the red reflector.

FIG. 10 describes points to be accumulated by a preceding vehicleextractor.

FIG. 11 is a functional block diagram for describing alight-distribution control of headlamps.

FIG. 12 is a top view for describing a relationship between a cut-offline angle and an angle of view.

FIG. 13A and FIG. 13B describe a table directed to the cut-off lineangles.

FIG. 14 describes an operation to be performed by a light-distributioncontroller.

FIG. 15A and FIG. 15B describe the light-distribution control based onan adaptive driving beam (ADB).

DETAILED DESCRIPTION

In the following, some preferred but non-limiting implementations of thetechnology are described in detail with reference to the accompanyingdrawings. Note that sizes, materials, specific values, and any otherfactors illustrated in respective implementations are illustrative foreasier understanding of the technology, and are not intended to limitthe scope of the technology unless otherwise specifically stated.Throughout the present specification and the drawings, elements havingsubstantially the same function and configuration are denoted with thesame reference numerals to avoid any redundant description. Further,elements that are not directly related to the technology areunillustrated in the drawings.

[Vehicle Exterior Environment Recognition System 100]

FIG. 1 is a block diagram illustrating a relationship of connection in avehicle exterior environment recognition system 100. The vehicleexterior environment recognition system 100 may include image-capturingunits 110, a vehicle exterior environment recognition apparatus 120, anda vehicle controller (e.g., an engine control unit (ECU)) 130. Theimplementation may include two image-capturing units 110 withoutlimitation.

The two image-capturing units 110 each may include an imaging devicesuch as, but not limited to, a charge-coupled device (CCD) and acomplementary metal-oxide semiconductor (CMOS). The image-capturingunits 110 each may capture an image of a vehicle exterior environmentahead of an own vehicle 1, and each may generate a luminance image thatcontains at least information on luminance. The luminance image may be acolor image or a monochrome image. The two image-capturing units 110 maybe so disposed that their respective optical axes become substantiallyparallel to each other along a traveling direction of the own vehicle 1.In addition, the two image-capturing units 110 may be so disposed as tobe separated away from each other in a substantially horizontaldirection. The image-capturing units 110 each may continuously generatethe luminance image for each frame of, for example but not limited to,1/60 second (at a frame rate of 60 fps). The luminance image may beobtained as a result of the image capturing performed on athree-dimensional object in a detection region that is ahead of the ownvehicle 1. In this implementation, the luminance images that aredifferent from each other in viewpoint are generated by the twoimage-capturing units 110, making it possible to sense a distance fromthe own vehicle 1 (the image-capturing units 110) to thethree-dimensional object. Note that the three-dimensional objects to berecognized by the image-capturing units 110 may include athree-dimensional object that is present independently and an object asa part of the independently-present three-dimensional object.Non-limiting examples of the independently-present three-dimensionalobject may include a vehicle (including a preceding vehicle and anoncoming vehicle), a pedestrian, a street light, a traffic light, a road(or a traveling path), a road sign, a guardrail, and a building.

The vehicle exterior environment recognition apparatus 120 may obtainthe luminance image from each of the two image-capturing units 110. Byobtaining the luminance images, the vehicle exterior environmentrecognition apparatus 120 may derive a parallax (a depth distance) and ascreen position with use of so-called pattern matching to thereby derivea three-dimensional position of each block. The screen positionindicates a position of any block in a screen. The pattern matching mayinvolve searching a block (as an aggregate of pixels) corresponding toany block extracted from one of the luminance images in the other of theluminance images. The vehicle exterior environment recognition apparatus120 may then identify the three-dimensional object present in thevehicle exterior environment, such as the preceding vehicle that travelsin the same direction as the own vehicle 1 and the oncoming vehicle thattravels closer to the own vehicle 1 in an oncoming fashion. Further,when the three-dimensional object is thus identified, the vehicleexterior environment recognition apparatus 120 may so control the ownvehicle 1 as to avoid collision with the three-dimensional object (i.e.,a collision avoidance control) or to keep an inter-vehicular distancebetween the own vehicle 1 and the preceding vehicle to a safe distance(i.e., a cruise control).

The vehicle exterior environment recognition apparatus 120 may alsoreceive a request (i.e., an intention) of a driver through anillumination switch 122, and perform, in accordance with the vehicleexterior environment, a light-distribution control of headlamps or anyother illuminator with use of an illumination mechanism 124.Non-limiting examples of the light-distribution control may include highbeam assist (HBA) and adaptive driving beam (ADB). The HBA may turn offhigh beams when the three-dimensional object in which application of thehigh beams is undesirable is present ahead of the own vehicle 1, andturn on the high beams when the irradiation-undesirablethree-dimensional object is not present ahead of the own vehicle 1.Non-limiting examples of the irradiation-undesirable three-dimensionalobject may include the preceding vehicle and the oncoming vehicle. TheADB may variably set regions to be irradiated with the high beams, andrefrain from applying the high beams only to the region in which theirradiation-undesirable three-dimensional object is present, and applythe high beams to the regions in which the three-dimensional objectsother than the irradiation-undesirable three-dimensional object, such asa street light, a road sign, a sign, and a reflector, are possiblypresent. To achieve the light-distribution control, a main switch and adimmer switch may be provided as the illumination switch 122. The mainswitch may switch positions of lighting states of the lamps from onelighting state position to another, and the dimmer switch may switchbetween a position in which the use of the high beams is not allowed anda position in which the use of the high beams is allowed. The lightingstates of the lamps may include off, small lamp (position lamp), on (lowbeams), and auto light. The illumination mechanism 124 may include amechanism that switches between the low beams and the high beams in oneimplementation where the light-distribution control is based on the HBA,and include a mechanism that variably sets the regions to be irradiatedwith the high beams in one implementation where the light-distributioncontrol is based on the ADB.

The vehicle controller 130 may control the own vehicle 1 by receivinginformation on an operation input of the driver through a steering wheel132, an accelerator pedal 134, and a brake pedal 136 and sending theinformation on the operation input to a steering mechanism 142, a drivemechanism 144, and a brake mechanism 146. The vehicle controller 130 maycontrol the steering mechanism 142, the drive mechanism 144, and thebrake mechanism 146, in accordance with instructions received from thevehicle exterior environment recognition apparatus 120.

For example, in order to perform the cruise control in relation to thepreceding vehicle and prevent the preceding vehicle and the oncomingvehicle from being irradiated with the high beams, it is desirable thatthe vehicle exterior environment recognition system 100 identify thepreceding vehicle and the oncoming vehicle promptly and accurately. Thevehicle exterior environment recognition system 100 according to oneimplementation may obtain information on three-dimensional positions andcolor information with use of the luminance images acquired from the twoimage-capturing units 110 to identify the preceding vehicle and theoncoming vehicle promptly and accurately, and thereby perform thelight-distribution control of the headlamps appropriately.

In the following, a description is given in detail of a configuration ofthe vehicle exterior environment recognition apparatus 120. Adescription is given here in detail of the light-distribution control ofthe headlamps as one of features of this implementation. Note that aconfiguration less related to the features of the implementation willnot be described in detail.

[Vehicle Exterior Environment Recognition Apparatus 120]

FIG. 2 is a functional block diagram illustrating schematic functions ofthe vehicle exterior environment recognition apparatus 120. Referring toFIG. 2, the vehicle exterior environment recognition apparatus 120 mayinclude an interface (I/F) 150, a data memory 152, and a centralcontroller 154.

The interface 150 may exchange information bilaterally between devicesincluding, without limitation, the image-capturing units 110 and thevehicle controller 130. The data memory 152 may include a random accessmemory (RAM), a flash memory, a hard disk drive (HDD), or any othersuitable storage device. The data memory 152 may store various pieces ofinformation necessary for processes to be carried out by the functionalblocks to be described hereinafter.

The central controller 154 may include a semiconductor integratedcircuit, and may control devices including, without limitation, theinterface 150 and the data memory 152 through a system bus 156. Thesemiconductor integrated circuit may have devices such as, but notlimited to, a central processing unit (CPU), a read only memory (ROM) inwhich programs, etc., are stored, and a random access memory (RAM)serving as a work area. In this implementation, the central controller154 may also function as an image processor 160, a three-dimensionalposition deriving unit 162, an integration value deriving unit 164, anecessity determiner 166, a detection range setter 168, a precedingvehicle extractor 170, a preceding vehicle recognizer 172, an oncomingvehicle extractor 174, an oncoming vehicle recognizer 176, a streetlight extractor 178, a street light recognizer 180, a traveling scenedeterminer 182, and a light-distribution controller 184. In thefollowing, a description is given in detail, together with an operationof each of such functional blocks, of a vehicle exterior environmentrecognition process that is directed to the light-distribution controlof the headlamps and is one of the features of this implementation.

[Vehicle Exterior Environment Recognition Process]

FIG. 3 is a flowchart illustrating an example of a flow of the vehicleexterior environment recognition process. In the vehicle exteriorenvironment recognition process, the image processor 160 may process theimages obtained from the two image-capturing units 110 (S200), thethree-dimensional position deriving unit 162 may derive thethree-dimensional positions from an image (S202), and the necessitydeterminer 166 may make a determination as to whether the high beams ofthe headlamps is necessary (S204). The vehicle exterior environmentrecognition process may end when a determination is made by thenecessity determiner 166 that the high beams are unnecessary (YES inS204).

When a determination is made by the necessity determiner 166 that thehigh beams are necessary (NO in S204), the detection range setter 168may set a detection range for each of the tail lamps, the headlamps, andthe street lights in the acquired image (S206), the preceding vehicleextractor 170 may extract the tail lamps from the preceding vehicledetection range (S208), and the preceding vehicle recognizer 172 mayrecognize the preceding vehicle (S210). In addition, the oncomingvehicle extractor 174 may extract the headlamps from the oncomingvehicle detection range (S212), and the oncoming vehicle recognizer 176may recognize the oncoming vehicle (S214). The street light extractor178 may extract the street lights from the street light detection range(S216), and the street light recognizer 180 may recognize the streetlights (S218). Further, the traveling scene determiner 182 may make adetermination, from information such as positional information of thestreet lights, as to whether a traveling scene is a traveling scene inwhich the application of the high beams is possible (S220), and thelight-distribution controller 184 may execute the light-distributioncontrol of the headlamps, on the basis of the preceding vehicle, theoncoming vehicle, and the traveling scene (S222). The vehicle exteriorenvironment recognition process may end following the execution of thelight-distribution control. In the following, a description is given indetail of each of the processes.

[Image Process S200]

The image processor 160 may obtain the luminance image from each of thetwo image-capturing units 110, and derive the parallax with use of theso-called pattern matching. The pattern matching may involve searching ablock corresponding to any block extracted from one of the luminanceimages in the other of the luminance images. The block may be, forexample but not limited to, an array of four horizontal pixels by fourvertical pixels. As used herein, the term “horizontal” refers to alateral direction of a screen of the captured image, and the term“vertical” refers to a vertical direction of the screen of the capturedimage.

As the pattern matching, a luminance (i.e., a Y color-difference signal)may be compared, between the two luminance images, per block thatindicates any image position. Non-limiting examples of such a luminancecomparison method may include SAD (Sum of Absolute Difference) thatobtains luminance differences, SSD (Sum of Squared intensity Difference)that uses the squared differences, and ZNCC (Zero-mean Normalized CrossCorrelation) that obtains similarity of variance obtained as a result ofsubtraction of an average luminance value from a luminance value of eachpixel. The image processor 160 may perform the foregoing parallaxderiving process, performed on a block basis, for all of the blocks inthe detection region. The detection region may be, for example but notlimited to, an array of 600 horizontal pixels by 180 vertical pixels. Inthis implementation, each block may include the array of four horizontalpixels by four vertical pixels; however, any number of pixels may be setfor each block.

The image processor 160 derives the parallax per block, i.e., derivesthe parallax on a detection resolution basis. However, the imageprocessor 160 may have difficulties in recognizing the block in terms ofwhich part of a three-dimensional object that block belongs and in termsof a type of that three-dimensional object. Hence, the parallax isderived independently on the detection resolution basis (e.g., on theblock basis) with respect to the detection region, not on athree-dimensional object basis. Note that the image, in whichinformation on the thus-derived parallax (equivalent to a depth distancez to be described later) is associated with the luminance images, ishereinafter referred to as a distance image.

FIG. 4A and FIG. 4B respectively describe the luminance image 212 andthe distance image 214. FIG. 4A describes a non-limiting example inwhich the luminance image 212 as illustrated in FIG. 4A is generated foran image region 216 by means of the two image-capturing units 110. Notethat FIG. 4A schematically illustrates only one of the two luminanceimages 212 generated by the respective image-capturing units 110 foreasier understanding. In this implementation, without limitation, theimage processor 160 may obtain the parallax for each of the blocks fromthe luminance images 212 to form the distance image 214 as illustratedin FIG. 4B. Each of the blocks in the distance image 214 may beassociated with the parallax of the corresponding block. For descriptionpurpose, each of the blocks for which the parallax is derived is denotedby a black dot.

[Three-Dimensional Position Deriving Process S202]

Thereafter, the three-dimensional position deriving unit 162 mayconvert, on the basis of the distance image 214 generated by the imageprocessor 160, the parallax information for each of the blocks in theimage region 216 into information on the three-dimensional position inreal space, with use of a so-called stereo method. The information onthe three-dimensional position may include pieces of information on ahorizontal distance x, a height y, and the depth distance (a relativedistance) z. The stereo method may involve deriving, from the parallaxin the distance image 214 of any part of the three-dimensional object (apixel or the block including the pixels), the depth distance z from theimage-capturing units 110 to that part of the three-dimensional objectwith use a triangulation method. Upon deriving the three-dimensionalposition, the three-dimensional position deriving unit 162 may derivethe height y from a road surface of any part of the three-dimensionalobject, on the basis of the depth distance z of the part of thethree-dimensional object and on the basis of a detection distance in thedistance image 214 from a point on the road surface to the part of thethree-dimensional object. The point on the road surface is located at aposition that is the same in depth distance z as the part of thethree-dimensional object. The three-dimensional position deriving unit162 may further associate the thus-derived three-dimensional positionwith the distance image 214 again. Note that various known techniquesmay be applied to the processes of deriving the depth distance z andidentifying the three-dimensional position and will not be described indetail.

[Necessity Determining Process S204]

Thereafter, the necessity determiner 166 may make a determination as towhether the outside of the own vehicle 1 is light, e.g., as to whetherthe time is day or night. Specifically, the necessity determiner 166 maymake a determination as to whether the high beams of the headlamps arenecessary. The processes from S206 to S222 directed to thelight-distribution control of the headlamps following the necessitydetermining process S204 may be skipped when a determination is made bythe necessity determiner 166 that the high beams are unnecessary, thusmaking it possible to reduce a processing load. Hereinafter, a state inwhich the high beams are unnecessary is simply referred to as a “highbeams unnecessary state”.

Incidentally, the image-capturing units 110 may include an unillustratedexposure amount adjuster that adjusts an exposure amount on the basis ofthe vehicle exterior environment. The exposure amount may be calculatedon the basis of sensitivity (a gain in this implementation withoutlimitation), aperture, and exposure time. For example, the exposureamount adjuster may use a luminance distribution of a region in a partof the generated image (for example, a road surface region) to decreasethe gain and the exposure time when a luminance of the region is high,and increase the gain and the exposure time when the luminance of theregion is low. In other words, the exposure amount adjuster may adjustthe gain and the exposure time so that the luminance suitable for therecognition of each of the various three-dimensional objects isobtained. Such an exposure amount adjuster may thus serve as anilluminance deriving unit that derives illuminance outside the ownvehicle 1, meaning that the illuminance is low when the exposure amountis large, and that the illuminance is high when the exposure amount issmall. In the following implementation, the illuminance outside the ownvehicle 1 is expressed by the exposure amount, and a threshold of theilluminance (an illuminance threshold) is expressed by a threshold ofthe exposure amount (an exposure threshold). However, the illuminanceand the illuminance threshold can be obviously based on, for example,illuminance obtained from an image and illuminance obtained from anilluminance sensor.

The necessity determiner 166 is thus able to sense the brightnessoutside the own vehicle 1 by referring to the exposure amount adjustedby the exposure amount adjuster of each of the image-capturing units110. For example, the necessity determiner 166 may compare the exposureamount with a predetermined threshold, and may determine that theoutside of the own vehicle 1 is light (i.e., the illuminance is high)and hence the high beams are not necessary (the high beams unnecessarystate) when the gain is small and the exposure time is short (i.e., theexposure amount is small), and determine that the outside of the ownvehicle 1 is dark (i.e., the illuminance is low) and hence the highbeams are available when the gain is large and the exposure time is long(i.e., the exposure amount is large). Hereinafter, a state in which thehigh beams are available is simply referred to as a “high beams allowedstate”.

However, simply comparing the exposure amount with the threshold maypossibly result in a concern that the lighting state of the headlampsbecomes unstable. This may possibly occur when the determination onwhether the state is the high beams unnecessary state or not is reversedfrequently (when chattering occurs in the determination) on a framebasis in accordance with a fluctuation of the gain, the exposure time,or both, for example. To address this, the present implementation mayaggregate, in time series, pieces of information that belong to arelatively long period of time, and make the determination on whetherthe state is the high beams unnecessary state on the basis of a resultof the aggregation. Specifically, the integration value deriving unit164 may derive an addition/subtraction value that is based on theexposure amount, and derive an integration value in which theaddition/subtraction value is integrated for each predetermined cycle(e.g., integrated for each frame). For example, the addition/subtractionvalue may be a value within a range from minus 15 (−15) to plus 15(+15), and the integration value may be in a range from 0 (zero) to10000. On the basis of the thus-derived integration value, the necessitydeterminer 166 may determine, for example, that the state is the highbeams unnecessary state when the integration value is small, and thatthe state is the high beams allowed state when the integration value islarge. Further, a threshold directed to comparison of the integrationvalue may involve a hysteresis characteristic to prevent the frequentreversal of the determination on whether the state is the high beamsunnecessary state or not.

FIG. 5 describes an example of a determination process to be performedby the necessity determiner 166. The integration value deriving unit 164may derive the negative addition/subtraction value when the exposureamount is less than the predetermined exposure threshold, and derive thepositive addition/subtraction value when the exposure amount is equal toor greater than the predetermined exposure threshold. For example, thepredetermined threshold may be a median of the exposure amount, such asa median of thresholds TH3 and TH4. Further, as illustrated in (a) ofFIG. 5, the integration value deriving unit 164 may so derive theaddition/subtraction value that the addition/subtraction value for theexposure amount that is larger than the exposure threshold becomeslarger in absolute value than the addition/subtraction value for theexposure amount that is smaller than the exposure threshold, when theintegration value is less than a predetermined third integrationthreshold. For example, the third integration threshold may be 5000.When the integration value is equal to or greater than the thirdintegration threshold, the integration value deriving unit 164 may soderive the addition/subtraction value that the addition/subtractionvalue for the exposure amount that is larger than the exposure thresholdbecomes smaller in absolute value than the addition/subtraction valuefor the exposure amount that is smaller than the exposure threshold.

In another respect, the integration value deriving unit 164 may soderive the addition/subtraction value that the addition/subtractionvalue for the exposure amount in which the integration value is lessthan the predetermined third integration threshold becomes larger inabsolute value than the addition/subtraction value for the exposureamount in which the integration value is equal to or greater than thepredetermined third integration threshold, when the exposure amount isequal to or greater than the predetermined exposure threshold. When theexposure amount is less than the predetermined exposure threshold, theintegration value deriving unit 164 may so derive theaddition/subtraction value that the addition/subtraction value for theexposure amount in which the integration value is less than thepredetermined third integration threshold becomes smaller in absolutevalue than the addition/subtraction value for the exposure amount inwhich the integration value is equal to or greater than thepredetermined third integration threshold. Here, TH1 to TH6 each denotea threshold within an exposure amount range whereTH1>TH2>TH3>TH4>TH5>TH6, meaning that the larger the value of thethreshold is, the darker the environment outside the own vehicle 1 is.

In this implementation, the threshold for the exposure amount is dividedfinely to set the addition/subtraction value individually for each ofthe exposure amounts, making it possible to achieve the followingexample features. In a situation where the environment outside the ownvehicle 1 makes a transition in brightness from light to dark (such as atransition from 4 pm to 8 pm) as illustrated in (b) of FIG. 5, theintegration value becomes closer to the third integration thresholddepending on the exposure amount as illustrated in (c) of FIG. 5, wherethe integration value is less than the third integration threshold (suchas 5000). Here, the absolute value of the addition/subtraction valueincreases with the increase in the exposure amount, meaning that theintegration value becomes closer to the third integration threshold morepromptly as the environment outside the own vehicle 1 is darker.However, when the integration value becomes equal to or greater than thethird integration threshold, the integration value remains near thethird integration threshold due to a decrease in increase rate of theintegration value where, for example, the exposure amount is less thanthe threshold TH1. Under such circumstances, when the environmentoutside the own vehicle 1 becomes sufficiently dark (i.e., the exposureamount ≥TH1) and thus the integration value becomes equal to or greaterthan a first integration threshold, the necessity determiner 166 maydetermine that the state is the high beams allowed state as illustratedin (d) of FIG. 5. For example, the first integration threshold may be6000.

With this configuration, the integration value may become 10000 under asufficiently-dark environment, may become 0 (zero) under asufficiently-light environment, and may become around 5000 under anenvironment in which the brightness lies about midway between thoseenvironments. Hence, the determination as to whether the state is thehigh beams unnecessary state is not performed for a slightly-darkenvironment, such as an environment in which the exposure amount is nearthe threshold TH3 or TH4. If, for example, the addition/subtractionvalue is derived solely on the basis of the determination as to whetherthe environment depending on the exposure amount is sufficiently lightor sufficiently dark regardless of the integration value, theintegration value does not increase (i.e., remains zero) until theenvironment becomes sufficiently dark in a situation where theenvironment makes a transition from day to night. In this case, it isnecessary to wait for the integration value to increase from 0 (zero) to6000 following the transition to the night. In contrast, according tothe present implementation, it is sufficient to wait for the integrationvalue to increase from 5000 to 6000 owing to the integration value whichis already increased to 5000 at the time of early evening, making itpossible to make the determination as to whether the state is the highbeams allowed state in a shorter time.

In a situation where the environment outside the own vehicle 1 makes atransition in brightness from dark (the integration value equals 10000)to light, the integration value becomes closer to the third integrationthreshold promptly as illustrated in (c) of FIG. 5. This is because, asillustrated in (a) of FIG. 5, the absolute value of theaddition/subtraction value is set to be larger as the exposure amountbecomes smaller (i.e., as the environment becomes lighter), and is setto be larger for a case where the integration value is large as comparedwith the third integration threshold than for a case where theintegration value is small as compared with the third integrationthreshold. However, when the integration value becomes less than thethird integration threshold, the integration value remains near thethird integration threshold due to a decrease in decrease rate of theintegration value where, for example, the exposure amount is equal to orgreater than the threshold TH6. Under such circumstances, when theenvironment outside the own vehicle 1 becomes sufficiently light (i.e.,the exposure amount <TH6) and thus the integration value becomes lessthan a second integration threshold, the necessity determiner 166 maydetermine that the state is the high beams unnecessary state asillustrated in (d) of FIG. 5. For example, the second integrationthreshold may be 4000. Thus, it is sufficient to wait for theintegration value to decrease from 5000 to 4000 owing to the integrationvalue which is already decreased to 5000 at dawn even if the environmentmakes a transition from night to day. Hence, it is possible to make thedetermination as to whether the state is the high beams unnecessarystate in a shorter time, as compared with a case where theaddition/subtraction value is derived solely on the basis of thedetermination as to whether the environment is sufficiently light orsufficiently dark in terms of the exposure amount regardless of theintegration value.

Further, the configuration is employed that causes the integration valueto remain near the third integration threshold and varies theaddition/subtraction value depending on whether the integration value isequal to or greater than the third integration threshold or less thanthe third integration threshold. This configuration prevents theintegration value from becoming equal to or greater than the firstintegration threshold unless the sufficiently-dark state continues. Thethird integration threshold is smaller than the first integrationthreshold and larger than the second integration threshold. Theconfiguration also prevents the integration value from becoming lessthan the second integration threshold unless the sufficiently-lightstate continues. Thus, it is possible to prevent unnecessary overturn inthe determination as to whether the state is the high beams unnecessarystate even upon passing shadows or passing through tunnels duringdaytime, or traveling through town during the night. Hence, it ispossible to achieve a stable determination result.

Note that the hysteresis characteristic is provided in the presentimplementation. Thus, the necessity determiner 166 may determine thatthe state is the high beams allowed state when the integration valuebecomes equal to or greater than the predetermined first integrationthreshold that may be, for example, 6000, and determine that the stateis the high beams unnecessary state when the integration value becomesless than the second integration threshold. The second integrationthreshold is smaller than the first integration threshold, and may be,for example, 4000. Hence, when the integration value becomes equal to orgreater than the first integration threshold and thus once the necessitydeterminer 166 determines that the state is the high beams allowedstate, no determination is made that the state is the high beamunnecessary state, i.e., no reversal in the determination is made, untilthe integration value becomes less than the second integrationthreshold. Likewise, when the integration value becomes less than thesecond integration threshold and thus once the necessity determiner 166determines that the state is the high beams unnecessary state, nodetermination is made that the state is the high beam allowed stateuntil the integration value becomes equal to or greater than the firstintegration threshold.

When the necessity determiner 166 determines that the state is the highbeams unnecessary state, the processes from S206 to S222 of thelight-distribution control of the headlamps following the necessitydetermining process S204 may be skipped as described above. This meansthat a preceding vehicle extracting process S208, a preceding vehiclerecognizing process S210, an oncoming vehicle extracting process S212,and an oncoming vehicle recognizing process S214 may not be executedduring continuation of the high beams unnecessary state. However, alight-distribution process of the headlamps may possibly become unstablewhen a transition is made from the high beams unnecessary state to thehigh beams allowed state and thus execution of the foregoing processesfrom S208 to S214 is started suddenly. In this regard, a possibility ofmaking the transition from the high beams unnecessary state to the highbeams allowed state is high even upon the high beams unnecessary statewhen the integration value is equal to or greater than a predeterminedvalue that may be, for example, 5500. Hence, to prevent the unstablelight-distribution process, the preceding vehicle extracting processS208, the preceding vehicle recognizing process S210, the oncomingvehicle extracting process S212, and the oncoming vehicle recognizingprocess S214 may be executed in advance as an advance preparation forstarting the light-distribution process of the headlamps.

As described above with reference to FIG. 5, the addition/subtractionvalue based on the exposure amount is integrated and the determinationon whether the state is the high beam unnecessary state is made on thebasis of the integration value, in the present implementation. In thefollowing (1) to (9), processes of varying the integration value and anyother factor depending on the vehicle exterior environment are describedin order to reflect the actual vehicle exterior environment more to theforegoing technique according to the present implementation.

(1) The time of the day is undetermined upon start of driving (start-up)of a vehicle. Hence, the integration value may be forcibly set to thethird integration threshold regardless of a value of the integrationvalue at that time. The third integration threshold may be, for example,5000. Further, regardless of the value of the integration value at thattime, the determination result may be set to indicate that the state isthe high beams unnecessary state. Here, the high beams unnecessary statemay be maintained when the state is already the high beams unnecessarystate, and the state may be switched to the high beam unnecessary statewhen the state is the high beam allowed state. With the configurationaccording to (1), it is possible to allow the necessity determiner 166to make the determination as to whether the state is the high beamsunnecessary state promptly.

(2) An auto light function of the vehicle may be utilized to vary theintegration value. As used herein, the term “auto light function” mayrefer to a function in which the headlamps are automatically lightedwhen a detection value obtained by the illuminance sensor is less than apredetermined illuminance threshold, i.e., when the brightness outsidethe own vehicle 1 becomes insufficient. The high beams are unnecessaryobviously in a situation where the automatic lighting of the headlampsis unnecessary. Thus, when the detection value obtained from theilluminance sensor for the auto light is equal to or greater than thepredetermined illuminance threshold, i.e., when the automatic lightingof the headlamps is unnecessary, the integration value at that time maybe forcibly set to the third integration threshold that may be 5000 in acase where the integration value at that time is equal to or greaterthan the third integration threshold. Further, the determination resultmay be set to indicate that the state is the high beams unnecessarystate. However, only the determination result may be set to indicatethat the state is the high beams unnecessary state without varying theintegration value in a case where the integration value at that time isless than the third integration threshold. With the configurationaccording to (2), it is possible to allow the necessity determiner 166to make the determination as to whether the state is the high beamsunnecessary state promptly.

It is to be noted that control systems of the illuminance sensor and theheadlamps may sometimes be independent from a control system of thevehicle exterior environment recognition apparatus 120 and thus a directreference to the detection value obtained from the illuminance sensormay involve difficulties in some cases. In such cases, instead of makingthe determination as to whether the detection value obtained from theilluminance sensor for the auto light is equal to or greater than thepredetermined illuminance threshold, the varying of the integrationvalue, the switching of the determination results, or both may beperformed on a condition that the auto light function is enabled (themain switch is at the auto light position) and that the low beams arenot turned on.

(3) Not only the main switch but also the dimmer switch may be utilizedto vary the integration value. For example, a situation where the dimmerswitch is set to the position in which the use of the high beams isallowed can be regarded as a driver's intention that the driver wishesto set the high beams for the headlamps. However, some drivers wish toenable the HBA or the ADB constantly and thus always keep the dimmerswitch to the position in which the use of the high beams is allowed. Inview of such circumstances, it is difficult to determine that the driverwishes to turn on the high beams solely by the fact that the dimmerswitch is at the position in which the use of the high beams is allowed.

To address this, a determination may be made that the driver intends toset the high beams for the headlamps not on the basis of the fact thatthe dimmer switch is routinely at the position in which the use of thehigh beams is allowed but on the basis of the fact that the dimmerswitch is switched from the position in which the use of the high beamsis not allowed to the position in which the use of the high beams isallowed. In other words, when the integration value is less than thepredetermined value, the integration value may be varied to thatpredetermined value upon switching of the dimmer switch from theposition in which the use of the high beams is not allowed to theposition in which the use of the high beams is allowed. Thepredetermined value may be equal to or greater than the thirdintegration threshold and less than the first integration threshold, andmay be, for example, 5500. The integration value may not be varied,i.e., may be maintained, when the integration value is equal to orgreater than the predetermined value. Note that a result of thedetermination as to whether the state is the high beams unnecessarystate is unchanged. In the process according to (3), information basedon hardware, i.e., the dimmer switch, is utilized, making it possible toachieve the process of varying the integration value without thenecessity of integrating the addition/subtraction value that is based onthe exposure amount. Specifically, it is possible to achieve the processof varying the integration value, by directly detecting the illuminanceoutside the own vehicle 1 with use of the illuminance sensor or anyother detector without using the image-capturing units 110 andintegrating the addition/subtraction value that is based on the detectedilluminance.

In the process according to (3), the predetermined value may be set to avalue that is equal to or greater than the third integration threshold,i.e., may be slightly less than the first integration threshold. Onereason is to promptly reflect the driver's intention to turn on the highbeams. Further, one reason that the predetermined value is less than thefirst integration threshold is to prevent rough determination that thestate is the high beams allowed state in a situation where, to enablethe HBA or the ADB during daytime, the dimmer switch is switched to theposition in which the use of the high beams is allowed. With theconfiguration according to (3), it is possible to allow the necessitydeterminer 166 to make the determination as to whether the state is thehigh beams unnecessary state promptly.

(4) The integration value may be varied when the vehicle exteriorenvironment is a particular environment. For example, in the cloudyearly morning, the exposure amount may possibly continue to be equal toor greater than the threshold TH6 illustrated in (a) of FIG. 5 for along time, which may possibly prevent prompt switching from the highbeams allowed state to the high beams unnecessary state. To addressthis, the integration value may be varied to the third integrationthreshold when the integration value is equal to or greater than thethird integration threshold, on a condition that the exposure amountcontinues to be less than a predetermined exposure threshold illustratedin (a) of FIG. 5 for a predetermined time threshold or more. Forexample, the predetermined exposure threshold may be the threshold TH5,and the predetermined time threshold may be a time period ranging from 5minutes to 10 minutes. The predetermined time threshold may be thenumber of frames corresponding to the time period. The integration valuemay not be varied when the integration value is less than the thirdintegration threshold. Note that, in either case, the determinationresult may be set to indicate that the state is the high beamsunnecessary state.

(5) The integration value may be varied when the vehicle exteriorenvironment is any other particular environment. As described above, theexposure amount adjuster may use a luminance distribution of a region ina part of the generated image (for example, a road surface region) toadjust the exposure amount. Under normal circumstances, the road surfaceoften has a color between gray and black. However, the road surfacebecomes white in a particular situation such as after snowfall and thusbecomes relatively high in luminance. Under such circumstances, therelationship “exposure amount ≥TH1” may possibly be met and thus thestate may possibly be determined as the high beams unnecessary stateeven in a sufficiently-dark situation in which the determination thatthe state is the high beams allowed state should be made.

To address this, other than the road surface region to which referenceis made to adjust the exposure amount, reference may be made to anyregion in the image and luminance of the region other than the roadsurface region may be obtained. For example, the region other than theroad surface region may be a region equivalent to the sky, and thereference may be made to 100 pixels in the region. Further, when theluminance of the region satisfies a predetermined darkness condition, 4(four) may be added to the integration value when the integration valueupon the satisfaction of the darkness condition is less than the thirdintegration threshold, and 2 (two) may be added to the integration valuewhen the integration value upon the satisfaction of the darknesscondition is equal to or greater than the third integration threshold.For example, the predetermined darkness condition may be a situationwhere the number of pixels, in which the luminance is less than apredetermined value (such as 10 on a scale from 1 to 256), is equal toor greater than a predetermined value (such as 90). Note that such aprocess may be carried out only when a predetermined condition issatisfied, such as when the exposure amount is equal to or greater thanthe threshold TH4. With the configuration according to (5), it ispossible to solve a concern, even for a snow-covered road surface duringthe night, that the state is determined continuously as being the highbeams unnecessary state for a long time unnecessarily.

(6) The process of integrating the integration value may be temporarilyhalted depending on the vehicle exterior environment. For example, whenan obstacle such as the preceding vehicle and the oncoming vehicle islocated immediately in front of the own vehicle 1, the exposure amountmay sometimes become small even during the night due to an influence oftail lamps and stop lamps of the preceding vehicle, or due to aninfluence of reflection of the headlamps, or any other factor, of theown vehicle 1. To address this, the three-dimensional position derivedfrom the image process S200 may be used to determine whether the depthdistance relative to the three-dimensional object immediately in frontof the own vehicle 1 is less than a predetermined distance threshold,and updating of the integration value, i.e., the integration of theintegration value, may not be performed when the depth distance relativeto the three-dimensional object immediately in front of the own vehicle1 is less than the predetermined distance threshold. The predetermineddistance threshold may be, for example, 10 meters.

Note that employing the process according to (6) may result in absenceof a variation in the integration value in a situation where theenvironment makes a transition from day to night upon a traffic jam.This, however, is unproblematic in that the high beams are unnecessaryin the first place when the preceding vehicle or any other obstacle islocated closely to the own vehicle 1. With the configuration accordingto (6), it is possible to prevent the state from being determinedunnecessarily as the high beams unnecessary state due to the influenceof the tail lamps and the stop lamps of the preceding vehicle, or due tothe influence of reflection of the headlamps, or any other factor, ofthe own vehicle 1.

(7) The process of integrating the integration value may be temporarilyhalted depending on the vehicle exterior environment in any othersituation. For example, when the own vehicle 1 stops at the front of anintersection during the night and thus the headlamps of the oncomingvehicle are bright, the exposure amount may sometimes become small dueto an influence of the headlamps of the oncoming vehicle. To addressthis, the updating of the integration value, i.e., the integration ofthe integration value, may not be performed when the own vehicle 1 isstopped and a determination is made that the oncoming vehicle is presentahead of the own vehicle 1. With the configuration according to (7), itis possible to prevent the state from being determined unnecessarily asthe high beams unnecessary state due to the influence of the headlampsof the oncoming vehicle.

(8) The process of integrating the integration value may be temporarilyhalted in any other situation. For example, even during the daytime, theexposure amount may possibly increase and thus the state may sometimesbe determined as the high beams allowed state irrespective of thevehicle exterior environment when the optical axes of theimage-capturing units 110 are interrupted. Further, the image-capturingunits 110 are susceptible to weather or any other factor and may involvedifficulties in recognizing the preceding vehicle, etc., due torainfall, fog, backlight, etc. To address this, the updating of theintegration value, i.e., the integration of the integration value, maynot be performed when a control performed by the image-capturing units110 is determined as being temporarily prohibited, i.e., determined as“HALT”. With the configuration according to (8), it is possible toprevent the state from being determined unnecessarily as the high beamsallowed state even in a situation where the image-capturing units 110fail to recognize the vehicle exterior environment normally.

(9) The thresholds of the exposure amount may be varied depending on thevehicle exterior environment. For example, the exposure amount maysometimes become small due to an influence of street lights when the ownvehicle 1 travels through an urban area. To address this, each of thethresholds TH1 to TH6 illustrated in (a) of FIG. 5 may be decreased by apredetermined rate while a current scene is determined as an urban areatraveling scene in a traveling scene determining process (S220)performed on a previous frame. The predetermined rate may be, forexample, 10%. With the configuration according to (9), it is possible toprevent the state from being determined unnecessarily as the high beamsunnecessary state due to the influence of street lights even upontraveling through the urban area.

[Detection Range Setting Process S206]

When a determination is made by the necessity determiner 166 that thestate is the high beams allowed state (NO in S204), the detection rangesetter 168 may take resources for processes of detecting, from theacquired image, the preceding vehicle (such as the tail lamps), theoncoming vehicle (such as the headlamps), and the street lights tothereby determine ranges in which the three-dimensional objects are tobe detected in more detail and with higher accuracy (i.e., detectionranges), in addition to a normal range directed to detection of thethree-dimensional objects. By limiting, within the image, the ranges inwhich the three-dimensional objects are to be detected in more detailand with higher accuracy in addition to the normal detection range ofthe three-dimensional objects in this way, it is possible to reduce aprocessing time required to extract the preceding vehicle, the oncomingvehicle, etc., and to prevent an erroneous detection in regions in whichpresence of the preceding vehicle, the oncoming vehicle, etc. isunlikely in terms of the nature of the region. In the following, adescription is given in detail of the detection ranges in which thethree-dimensional objects are to be detected in more detail and withhigher accuracy.

FIG. 6 is an explanatory view for describing the detection ranges. Thedetection range setter 168 may respectively set, at respectivepredetermined positions in the image region 216 which are illustrated inFIG. 6, a preceding vehicle detection range 220 a, an oncoming vehicledetection range 220 b, and a street light detection range 220 c to thepreceding vehicle, the oncoming vehicle, and the street lights eachserving as a detection target. Note that the preceding vehicle detectionrange 220 a, the oncoming vehicle detection range 220 b, and the streetlight detection range 220 c are respectively denoted by a rectangularbroken line, a rectangular one-dot chain line, and a rectangular two-dotchain line. As can be appreciated from FIG. 6, the preceding vehicledetection range 220 a is included in the oncoming vehicle detectionrange 220 b. It can also be appreciated from FIG. 6 that the precedingvehicle detection range 220 a and the oncoming vehicle detection range220 b are exclusive with respect to the street light detection range 220c.

The preceding vehicle detection range 220 a, the oncoming vehicledetection range 220 b, and the street light detection range 220 c may beoffsetable depending on the vehicle exterior environment, a travelingpath, or any other factor. For example, when a road is curved or has agradient, the preceding vehicle detection range 220 a, the oncomingvehicle detection range 220 b, and the street light detection range 220c may be offset depending on a level of the curve or the gradient. In anexample where the traveling path is a left-hand curve, the detectionrange setter 168 may offset each of the preceding vehicle detectionrange 220 a, the oncoming vehicle detection range 220 b, and the streetlight detection range 220 c to the left by an amount corresponding tothe level of the curve of that traveling path. With this configuration,it is possible to set, as the detection ranges, respective positions inwhich presence of the preceding vehicle, presence of the oncomingvehicle, and presence of the street lights are most likely.

[Preceding Vehicle Extracting Process S208]

Thereafter, the preceding vehicle extractor 170 may extract the taillamps from the preceding vehicle detection range 220 a on the basis of aluminance, color information, and a three-dimensional position. Notethat the tail lamps of the preceding vehicle are different in lightamount from the headlamps of the oncoming vehicle and the street lightsas described later. Under such circumstances, when images of the taillamps are captured by the image-capturing units 110 on the basis of anexposure time that is directed to acquiring of the images of the taillamps, the luminance of each of the headlamps and the street lights issaturated. Further, under such circumstances, capturing the images ofthe tail lamps by the image-capturing units 110 on the basis of anexposure time that is directed to acquiring of the images of theheadlamps and the street lights leads to failure in detection of thetail lamps. To address these, the image-capturing units 110 maygenerate, at different frames, the images on the basis of at least twoexposure times, i.e., a long exposure time and a short exposure time.

FIG. 7A and FIG. 7B describe the luminance images 212 that are differentfrom each other in exposure time. FIG. 7A illustrates an example of theluminance image 212 generated on the basis of the long exposure time,and FIG. 7B illustrates an example of the luminance image 212 generatedon the basis of the short exposure time. Hence, use of the luminanceimage 212 illustrated in FIG. 7A involves a possibility that theluminance of each of the headlamps and the street lights is saturatedbut makes it possible to properly extract the tail lamps, whereas use ofthe luminance image 212 illustrated in FIG. 7B involves a possibilitythat the tail lamps are unextractable but makes it possible to properlyextract the headlamps and the street lights.

The preceding vehicle extractor 170 may also perform grouping of thepixels in the preceding vehicle detection range 220 a. Specifically, thepreceding vehicle extractor 170 may perform the grouping of the pixelsin the preceding vehicle detection range 220 a by collecting the pixelsthat satisfy conditions, i.e., the pixels in which their respectivepieces of color information (RGB or YUV) fall within a predeterminedcolor range that indicates red, and in which their respectivethree-dimensional positions are within a predetermined distance range(such as falls within 1.5 pixels) with respect to each other. Here, thepreceding vehicle extractor 170 may perform grouping of the pixelslocated within a rectangular region. The rectangular region may bedefined by horizontal lines and vertical lines, and include all of thepixels that satisfy the foregoing conditions. The thus-grouped pixelsmay be handled as a tail lamp candidate that serves as a candidateidentifiable as the tail lamp. The tail lamp candidate following thegrouping may contain basic characteristic amounts such as: coordinatesof left, right, top, and bottom parts of the group, i.e., coordinates offour corners of the group; the number of pixels in the group; a maximumluminance value in the group; a minimum luminance value in the group,and an average depth distance, i.e., an average parallax, of the group.

In the present implementation, the preceding vehicle extractor 170 mayexclude the grouped pixels from the tail lamp candidate when the groupedpixels satisfy any of the following exclusion conditions. For example,the exclusion conditions may include: a difference (a size) between thecoordinates of the left, right, top, and bottom parts of the group whichis equal to or less than a predetermined value (for example, 2 pixels);a difference (a size) between the coordinates of the left, right, top,and bottom parts of the group which is equal to or greater than apredetermined value (which may be determined by the depth distance); andthe number of pixels in the group which is equal to or less than apredetermined value (for example, 2).

Note that a red reflector may sometimes be included in the precedingvehicle detection range 220 a in addition to the tail lamps. In thiscase, it is difficult to distinguish between the tail lamps and the redreflector solely on the basis of the color information. However, thetail lamps each become higher in luminance than the red reflector underthe condition where the depth distance is the same, due to a differencethat the red reflector utilizes light reflection whereas the tail lampseach emit light by itself. In the present implementation, suchcharacteristics are utilized to distinguish between the tail lamps andthe red reflector.

FIG. 8 describes a relationship between the tail lamp and the redreflector. As can be appreciated from FIG. 8, the luminance of the taillamp denoted by a solid line and the luminance of the red reflectordenoted by a broken line each decrease with an increase in the depthdistance. However, it can also be appreciated from FIG. 8 that the taillamp is higher in luminance than the red reflector at any depthdistance. For description purpose, a relationship between the depthdistance and the luminance is illustrated linearly in FIG. 8; however,the relationship is often nonlinear in practice. The preceding vehicleextractor 170 may exclude the grouped pixels from the tail lampcandidate, when the preceding vehicle extractor 170 determines, on thebasis of the depth distance and the luminance of the tail lampcandidate, that the relationship of the depth distance and the luminancecorresponds to the relationship according to the red reflectorillustrated in FIG. 8.

As described above, the tail lamps are extracted from the precedingvehicle detection range 220 a in the present implementation. However,the depth distance in the preceding vehicle detection range 220 a can beextremely long, e.g., may range from zero meter to hundreds of meters,and thus it is necessary to make the exposure time long in order torecognize the tail lamps far away from the own vehicle 1. Under suchcircumstances, it is possible to identify the relationship between thedepth distance and the luminance and thus the grouped pixels may bedistinguishable as, for example, the red reflector, for the tail lampslocated in a region A in which the depth distance is relatively long.For the tail lamps located in a region B in which the depth distance isshort, however, the luminance is saturated to the maximum as illustratedin FIG. 8 and thus the relationship between the depth distance and theluminance is unidentifiable. Note that the tail lamp candidate itself isextractable, due to a fact that a part at which the luminance saturatesis a light-emitting part of the tail lamp and a red part is stillpresent around the light-emitting part.

Further, the tail lamps are lower in luminance than the headlamps of theoncoming vehicle, meaning that the difference in luminance between thetail lamps and the red reflector is small in the first place. Thus, inthe region B of FIG. 8, the decrease in the luminance difference betweenthe tail lamps and the red reflector with the decrease in the depthdistance eventually results in the luminance saturation for both thetail lamps and the red reflector. Hence, the tail lamps and the redreflector may become indistinguishable from each other in a situationwhere the depth distance is short as described above.

Note that the red reflector is used not only as a display that callsdriver's attention while driving but also as a reflector for a vehicle.It is therefore desirable that the high beams be applied to a vehicle inwhich the tail lamps are unlighted, such as a parked vehicle, whilepreventing the running preceding vehicle from receiving glare attributedto the high beams.

To give one example, parallel parking on a road is common in residentialarea in the United States, meaning that an erroneous detection of thered reflector and the tail lamps may possibly raise a concern, forexample, that the high beams may not be turned on at a place with manyvehicles parked on the road, or that hunting occurs in which the highbeams and the low beams are switched in an alternating fashionrepeatedly. To avoid such circumstances, one method may be to utilize ashape of the tail lamp candidate. Another method may be to utilize aspeed (≠0) of the tail lamp candidate. The former, however, involvesdifficulties in that the red reflector is often not excludable by meansof the shape, whereas the latter involves difficulties in performinghighly accurate recognition due to, for example, the presence ofpreceding vehicle that remains stationary.

In conclusion, it is desirable that the tail lamps and the redreflectors be distinguished on the basis of the relationship between thedepth distance and the luminance. Thus, as described above, the presentimplementation uses, in addition to the luminance image 212 illustratedby way of example in FIG. 7A which is directed to the extraction of thetail lamps and based on the long exposure time, the luminance image 212illustrated by way of example in FIG. 7B which is directed to theextraction of the headlamps and the street lights and generated at theframe different from the frame at which the luminance image 212 of FIG.7A is generated.

FIG. 9 is another explanatory diagram for describing the relationshipbetween the tail lamps and the red reflector. The preceding vehicleextractor 170 may first use the luminance image 212 of FIG. 7A.Hereinafter, the luminance image 212 illustrated by way of example inFIG. 7A is referred to as a first luminance image 212. The firstluminance image 212 has a relationship between the luminance and thedepth distance of the block (i.e., the block of the tail lamp candidate)as illustrated in (a) of FIG. 9, making it possible to distinguishbetween the tail lamps and the red reflector on the basis of theluminance and the depth distance of the block and extract the tail lampsof the preceding vehicle, for a region A.

When the depth distance of the block is less than a predetermineddistance threshold, the preceding vehicle extractor 170 may use theluminance image 212 of FIG. 7B which is shorter in exposure time thanthe first luminance image 212. Hereinafter, the luminance image 212illustrated by way of example in FIG. 7B is referred to as a secondluminance image 212. The predetermined distance threshold may be, forexample, 150 meters. The second luminance image 212 has a relationshipbetween the luminance and the depth distance of the block as illustratedin (b) of FIG. 9, making it possible to distinguish between the taillamps and the red reflector on the basis of the luminance and the depthdistance of the block and extract the tail lamps of the precedingvehicle, also for a region B that is shorter in depth distance than theregion A.

For the preceding vehicle detection range 220 a used upon the extractionof the tail lamps from the second luminance image 212 that is based onthe short exposure time, the preceding vehicle detection range 220 aused upon the extraction of the tail lamps from the first luminanceimage 212 that is based on the long exposure time may be utilized as itis, or may be utilized after being slightly enlarged by, for example,1.1 times. Specifically, as the preceding vehicle detection range 220 a,the tail lamps are to be extracted from a range based on thealready-derived preceding vehicle detection range 220 a in the secondluminance image 212 that is based on the short exposure time. In thisregard, a position of the preceding vehicle moves little between framesowing to the sufficiently-high frame rate and a small relative speedbetween the preceding vehicle and the own vehicle 1. Hence, it ispossible to use, in a diverted fashion, the preceding vehicle detectionrange 220 a also for the luminance image 212 that is based on thedifferent frame without raising a concern. With this configuration, itis possible to avoid the necessity of performing the derivation of thepreceding vehicle detection range 220 a again and thereby to reduce aprocessing load.

In the following, a description is given of a specific but non-limitingprocess in which the preceding vehicle extractor 170 extracts the taillamps from the second luminance image 212 that is based on the shortexposure time. First, the preceding vehicle extractor 170 may use amaximum value of a red component of the tail lamp candidate (e.g., an Rcomponent among RGB components) as a characteristic amount of the taillamp. A calculation of the maximum value may be performed only on thepixels that satisfy a condition of “R≥G and R≥B”.

Further, a value accumulated on the basis of scores over a plurality offrames may be used in order to address variations in brightness of thetail lamp which may occur depending on types of vehicles andenvironments. Specifically, a tail lamp point and a non tail lamp pointmay be accumulated for each frame. The tail lamp point indicateslikelihood that the tail lamp candidate is the tail lamp, and the nontail lamp point indicates likelihood that the tail lamp candidate is notthe tail lamp. The tail lamp point and the non tail lamp point each maybe set to 0 (zero) for its initial value.

FIG. 10 describes the points to be accumulated by the preceding vehicleextractor 170. As can be appreciated from FIG. 10, four regions (a) to(d) may be set on the basis of the relationship in depth distance andluminance between the tail lamp and the red reflector as illustrated in(b) of FIG. 9. In the present implementation, the hatched region (b)equivalent to the relationship between the depth distance and theluminance of the tail lamp may be used to determine that it is likelythat the tail lamp candidate is the tail lamp, and the cross-hatchedregion (d) equivalent to the relationship between the depth distance andthe luminance of the red reflector may be used to determine that it isnot likely that the tail lamp candidate is the tail lamp. Further, theregion (c) between the regions (b) and (d) may be used to determine thatthe likelihood of the tail lamp candidate is uncertain, and the region(a) in which the luminance is higher than the luminance in the region(b), i.e., the luminance is high to the extent of the luminance of thestop lamp, may be used to determine that it is most likely that the taillamp candidate is the tail lamp. Note that the regions are illustratedlinearly with respect to the depth distance for convenience ofdescription in FIG. 10; however, the depth distance may be divided intoa plurality of depth distances to allow those regions to be discretized(to be provided stepwise) for each of the depth distances.

The preceding vehicle extractor 170 may add 5 points to the tail lamppoint when the relationship between the depth distance and the luminanceof the tail lamp candidate (the block) is determined as falling in theregion (a), and may add 1 (one) point to the tail lamp point when therelationship between the depth distance and the luminance of the taillamp candidate (the block) is determined as falling in the region (b).The preceding vehicle extractor 170 may refrain from performing anyprocess when the relationship between the depth distance and theluminance of the tail lamp candidate (the block) is determined asfalling in the region (c), and may add 1 (one) point to the non taillamp point when the relationship between the depth distance and theluminance of the tail lamp candidate (the block) is determined asfalling in the region (d). The tail lamp point and the non tail lamppoint thus calculated may be used in the preceding vehicle recognizingprocess S210 to be described later. Specifically, the tail lamp pointand the non tail lamp point may be used upon correction of thedetermined preceding vehicle after a determination is made by thepreceding vehicle recognizer 172 that a candidate identifiable as thepreceding vehicle, i.e., a preceding vehicle candidate, is the precedingvehicle. The correction of the preceding vehicle is described in greaterdetail later in “Preceding Vehicle Recognizing Process S210”.

Note that the tail lamps and the later-described headlamps are extractedon the basis of the characteristic amount in the images such as theluminance and the color information. In the following, a description isgiven based on the tail lamps for simplification purpose. When thecharacteristic amount fluctuates around its threshold, the extraction ofthe tail lamps itself may possibly become unstable. For example, asituation may possibly occur repeatedly in which tail lamps of theactual preceding vehicle are determined as being the tail lamps at anyframe but are determined as not being the tail lamps at any other frame.The unstable extraction of the tail lamps in this manner may possiblybring about the hunting in which the high beams and the low beams areswitched in an alternating fashion repeatedly for the light-distributioncontrol of the headlamps of the own vehicle 1.

Further, the three-dimensional object that does not emit light byitself, such as a reflector located in the vicinity of a traveling path,may cause a variation in characteristic amount in the images dependingon how that three-dimensional object is irradiated with light of theheadlamps of the own vehicle 1. This possibly makes it easier to causean erroneous detection of the three-dimensional object as the tail lamps(i.e., the preceding vehicle) or the headlamps (i.e., the oncomingvehicle). For example, in a situation where the own vehicle 1 is set toapply the high beams and the three-dimensional object may be erroneouslydetected as being the tail lamps (the preceding vehicle) due to thereflection of the high beams from the three-dimensional object, the highbeams are switched to the low beams to prevent the application of thehigh beams to the preceding vehicle. However, the switching from thehigh beams to the low beams makes the reflection of the high beamsdisappear, allowing the three-dimensional object to be no longerrecognized as the tail lamps. When the three-dimensional object is nolonger recognized as the tail lamps, the own vehicle 1 is set to applythe high beams again, resulting in the possible occurrence of hunting.

To address the possible occurrence of hunting, one method may be toperform countermeasures on the light-distribution control after therecognition of the preceding vehicle, the oncoming vehicle, or both.However, the light-distribution control itself may have to be madecomplex when the recognition as a basis of the light-distributioncontrol itself is unstable, leading to a lack of robustness.

Hence, the present implementation may perform, at the time of theextraction of the tail lamps or other illuminators, a process thatcombines the recognition process with a hysteresis characteristic.Specifically, the present implementation may change thresholds used tocompare the characteristic amount, depending on whether a target to beextracted is irradiated with the high beams.

For example, the threshold may be set higher, i.e., more stringent, fora region irradiated with the high beams than for a region not irradiatedwith the high beams to prevent the erroneous detection of the tail lampsor other illuminators. Alternatively, the threshold may be set lower,i.e., more flexible, for the region not irradiated with the high beamsthan for the region irradiated with the high beams to allow for easierdetection of the tail lamps or other illuminators. With thisconfiguration, it is possible to extract the tail lamps or otherilluminators appropriately and prevent the occurrence of hunting.

To change the thresholds depending on whether the target to be extractedis irradiated with the high beams, the region irradiated with the highbeams is determined first.

FIG. 11 is a functional block diagram for describing thelight-distribution control of the headlamps. In the presentimplementation, the preceding vehicle extractor 170 and the oncomingvehicle extractor 174 may respectively extract the tail lamps and theheadlamps. The preceding vehicle recognizer 172 and the oncoming vehiclerecognizer 176 may respectively recognize the preceding vehicle and theoncoming vehicle on the basis of the extracted tail lamps and theextracted headlamps. The light-distribution controller 184 maydetermine, on the basis of information obtained from the recognition,distribution of light of the headlamps, i.e., a range of application ofthe high beams or the necessity of the application of the high beams.The illumination mechanism 124 may apply the high beams, on the basis ofthe application range of the high beams obtained through controller areanetwork (CAN) communication denoted by a broken line.

Note that a delay in the CAN communication or any other factor maybecome an influential factor as described below, if the precedingvehicle extractor 170 acquires, through the CAN communication as denotedby the broken line in FIG. 11, result information regarding whichapplication range the illumination mechanism 124 has applied the highbeams and changes the thresholds as described above on the basis of theacquired result information.

To give one example, the light-distribution controller 184 transmits,when recognizing the preceding vehicle, instructions on switching of thestates of the headlamps from the high beams to the low beams for theregion in which the preceding vehicle is recognized. The illuminationmechanism 124 switches the states of the headlamps from the high beamsto the low beams in accordance with the instructions. However, due tothe delay in CAN communication performed from the light-distributioncontroller 184 to the illumination mechanism 124 and from theillumination mechanism 124 to the preceding vehicle extractor 170, thepreceding vehicle extractor 170 and the oncoming vehicle extractor 174do not receive the instructions yet and thus only have past informationthat the application of the high beams is currently carried out by theillumination mechanism 124 at the time when the light-distributioncontroller 184 has issued the instructions on the switching of thestates of the headlamps from the high beams to the low beams.

The foregoing example may possibly result in a situation that, even forthe subsequent frame, the preceding vehicle extractor 170 extracts thetail lamps while the threshold for the relevant region is still high, onthe basis of the past information that the headlamps are set to the highbeams. In this situation, the extracted tail lamps may possibly be lostin the subsequent frame.

To address this, the preceding vehicle extractor 170 acquires the resultinformation regarding which application range the illumination mechanism124 has applied the high beams through the CAN communication asillustrated by the broken line in FIG. 11. The preceding vehicleextractor 170 also acquires, as denoted by a one-dot chain line in FIG.11, information regarding which application range the light-distributioncontroller 184 has instructed a recipient to apply the high beams.Further, the preceding vehicle extractor 170 may change the thresholdsby using both the pieces of information together.

Specifically, the preceding vehicle extractor 170 recognizes that theapplication range is a region to which the low beams are to be applied(i.e., the high beams are not to be applied), when either one of theresult information regarding which application range the illuminationmechanism 124 has applied the high beams (i.e., information executed bythe illumination mechanism 124) and the information regarding whichapplication range the light-distribution controller 184 has instructedthe recipient to apply the high beams (i.e., information on theinstructions issued by the light-distribution controller 184) indicatesthe application of the low beams (i.e., when none of them indicates theapplication of the high beams). For example, the preceding vehicleextractor 170 determines that the low beams are applied when either ofthose pieces of information indicates the application of the low beamsin a case of the HBA. In a case of the ADB, the preceding vehicleextractor 170 determines that the low beams are applied when either ofthose pieces of information indicates the application of the low beamsfor any of angular ranges (i.e., any of angular regions).

With this configuration, it is possible to continue the detection of thepreceding vehicle, the oncoming vehicle, or both in a stable manner byusing a low value, i.e., a flexible value, for the threshold. This ispossible, for one reason to be discussed below, even in the situationwhere the result information regarding which application range theillumination mechanism 124 has applied the high beams still indicatesthe application of the high beams due to the delay in CAN communicationor any other factor following the change of the states of the headlightsfrom the high beams to the low beams. One reason is that the informationregarding which application range the light-distribution controller 184has instructed the recipient to apply the high beams indicates theapplication of the low beams, i.e., does not indicate the application ofthe high beams. Hence, it is possible to reduce a possibility that thepreceding vehicle (or the oncoming vehicle) is irradiated with the highbeams.

Note that, in a case of the ADB, the information regarding whichapplication range the illumination mechanism 124 has applied the highbeams is obtained from information on a cut-off line angle. The cut-offline angle information may be transmitted from the illuminationmechanism 124 and indicate an angle of application of the high beams.However, sole use of the cut-off line angle information may involvedifficulties in identifying, in a simple fashion, which range in theluminance images 212 the high beams are applied.

FIG. 12 is a top view for describing a relationship between the cut-offline angle and an angle of view. FIG. 12 illustrates an example in whichA and B are present at any same angle of view. In terms of the cut-offline angle, A and B are equal to each other in horizontal position inthe luminance images 212 generated by the image-capturing units 110.However, A is irradiated with the high beams as denoted by hatching,whereas B is not irradiated with the high beams. This is due to adifference in position between the image-capturing units 110 and theheadlamps (i.e., the illumination mechanisms 124) as illustrated in FIG.12. Hence, as long as the depth distance of any block is sensed, it ispossible for the preceding vehicle extractor 170 to determine, fromgeometric calculation, which range (i.e., block) in the luminance images212 the high beams are applied as illustrated in FIG. 12, on the basisof the angle of view of that block and the depth distance of that blockand the cut-off line angle.

Note that calculating whether the range (i.e., the block) is irradiatedwith the high beams on the basis of the angle of view and the depthdistance of the block and the cut-off line angle as illustrated in FIG.12 may incur an increase in processing load such as performingcalculation based on trigonometric function and division. To addressthis, the present implementation may divide a distance range defined bythe depth distance into a plurality of distance ranges and use a tablefor the respective distance ranges to reduce the processing load.

FIG. 13A and FIG. 13B describe a table directed to the cut-off lineangles. FIGS. 13A and 13B illustrate an example in which a distancerange defined by the depth distance is divided into 5 distance rangesand each of the distance ranges is associated with the single cut-offline angle. For example, the distance range defined by the depthdistance may be divided into a distance range that ranges from 0 meterto 10 meters, a distance range that ranges from 10 meters to 30 meters,a distance range that ranges from 30 meters to 70 meters, a distancerange that ranges from 70 meters to 200 meters, and a distance rangethat ranges from 200 meters onward. The cut-off line angle here may haveresolution of, for example, 0.1 degrees. In the following, a descriptionis given by referring to a comparison between the cut-off line anglebased on the depth distance of 10 meters and the cut-off line anglebased on the depth distance of 30 meters, each of which is denoted by abroken line in FIG. 13A. It can be appreciated from FIG. 13A that thecut-off line angles widen as the depth distance become short.

Hence, the present implementation may use the cut-off line angle basedon the depth distance of 10 meters (which may have 24.9 degrees in thepresent implementation without limitation) as illustrated in FIG. 13Bfor the cut-off line angle in the images which ranges from the distancerange of 10 meters to the distance range of 30 meters. The cut-off lineangle based on the depth distance of 10 meters involves the shortestdepth distance denoted by the broken line. Setting the cut-off lineangle that is wider than the real cut-off line angle for all of thedistance ranges defined by the depth distance, including the distancerange that ranges from 10 meters to 30 meters as well, makes it possibleto reduce a possibility that the preceding vehicle is irradiated withthe high beams.

Note that the five distance ranges are not divided equally but are sodivided that the distance ranges change nonlinearly as illustrated inFIG. 13B. One reason is that a difference between the cut-off line anglein the images and the real cut-off line angle increases sharply as thedepth distance becomes short. Changing the distance ranges nonlinearlyin this way makes it possible to set the appropriate cut-off line anglesthat are based on the depth distance.

As described above, the preceding vehicle extractor 170 may determinewhether any block is irradiated with the high beams on the basis of theangle of view of that block and the depth distance of that block in theimages and the cut-off line angle of the high beams. Further, thepreceding vehicle extractor 170 may change, on the basis of a result ofthe determination, the thresholds directed to the determination as towhether the tail lamp is the tail lamp. The preceding vehicle extractor170 may thereby extract the tail lamps of the preceding vehicle. Thepreceding vehicle recognizer 172 may recognize the preceding vehicle asdescribed later on the basis of a result of the extraction.

Note that a situation may sometimes arise where a half of the precedingvehicle in a horizontal direction is irradiated with the high beams andthe other half of the preceding vehicle in the horizontal direction isnot irradiated with the high beams, due to a width of the precedingvehicle which extends in the horizontal direction to some extent, forexample. In such a situation, a determination may be made on the basisof a rate of the application of the high beams. Specifically, acomparison may be made, with respect to the preceding vehicle candidate,between a rate in which the high beams are applied and a rate in whichthe high beams are not applied, and the determination may be made on thebasis of the larger rate. Hence, for example, a determination may bemade that the preceding vehicle candidate as a whole is irradiated withthe high beams when the rate in which the high beams are applied ishigh, and a determination may be made that the preceding vehiclecandidate as a whole is not irradiated with the high beams when the ratein which the high beams are not applied is high.

Incidentally, a determination can be made that the preceding vehiclecandidate as a whole is not irradiated with the high beams when it isuncertain as to whether the preceding vehicle candidate as a whole isnot irradiated with the high beams. In the present implementation,however, the table may be used to allow the cut-off line angles to bewider than the real cut-off line angles and thus to allow thedetermination to be made more easily that the high beams are not appliedas described above. Hence, to prevent making a determination that thepreceding vehicle candidate as a whole is not irradiated with the highbeams too often, whether or not the preceding vehicle candidate as awhole is irradiated with the high beams may be determined in the presentimplementation simply depending on the rates of the application of thehigh beams.

With this configuration, it is possible to prevent the occurrence ofhunting between the high beams and the low beams and thereby reduce thepossibility that the preceding vehicle is irradiated with the highbeams.

As described above, upon performing the light-distribution control ofheadlamps, it is desirable that the tail lamps of the preceding vehiclebe identified accurately to prevent the preceding vehicle from beingirradiated with the high beams. However, when a characteristic amount ofthe tail lamps fluctuates near a threshold, the extraction of the taillamp itself becomes unstable, bringing about, in some cases, the huntingin which the high beams and the low beams are switched in an alternatingfashion repeatedly. Further, the three-dimensional object that does notemit light by itself becomes high in luminance when the object isirradiated with light of the headlamps of the own vehicle, and becomeslow in luminance when the object is not irradiated with the light. Thisalso makes the extraction of the tail lamp itself unstable, bringingabout the hunting in some cases. To prevent erroneous detection of thetail lamp, one measure may be to set a threshold directed to theextraction of the tail lamp to be higher, i.e., more stringent, for aregion irradiated with the high beams than for a region not irradiatedwith the high beams. However, upon switching states of the headlampsfrom the high beams to the low beams, the threshold directed to asituation where the region is irradiated with the high beams may be usedeven though the three-dimensional object is no longer irradiated withthe high beams, due to a delay in communication performed in a vehicle.In this case, the three-dimensional object may possibly be determined onthe basis of the erroneous threshold. In contrast, according to oneimplementation of the technology, the preceding vehicle extractor 170acquires the result information regarding which application range theillumination mechanism 124 has applied the high beams, and also acquiresthe information regarding which application range the light-distributioncontroller 184 has instructed the recipient to apply the high beams.Further, the preceding vehicle extractor 170 may change the thresholdsby using both the pieces of information together. Hence, it is possiblefor the vehicle exterior environment recognition apparatus 120 toappropriately set the threshold, and thus to increase identificationaccuracy of the tail lamps of the preceding vehicle.

[Preceding Vehicle Recognizing Process S210]

Thereafter, the preceding vehicle recognizer 172 may perform grouping ofthe tail lamps extracted by the preceding vehicle extractor 170, andrecognize the preceding vehicle in the preceding vehicle detection range220 a.

Specifically, the preceding vehicle recognizer 172 may perform thegrouping of the tail lamps and recognize the grouped tail lamps as thepreceding vehicle candidate when all of the following conditions aresatisfied. For example, the conditions may include: whether a distancein the images between the tail lamps (the groups) falls within adistance range in which those tail lamps are determinable as belongingto the same vehicle, e.g., whether the distance is longer than thepredetermined distance range in the preceding vehicle extracting processS208; whether a difference in the average depth distance (the averageparallax) of the tail lamps falls within a distance range in which thosetail lamps are determinable as belonging to the same vehicle; andwhether a proportion of the maximum luminance value falls within apredetermined range.

The thus-grouped preceding vehicle candidate may take over the basiccharacteristic amounts of the tail lamps before the grouping. Forexample, coordinates of left, right, top, and bottom parts of thepreceding vehicle candidate, i.e., coordinates of four corners of thepreceding vehicle candidate, may take over coordinates that areequivalent to those located outward of the preceding vehicle candidateamong coordinates of left, right, top, and bottom parts of each of thetail lamps, i.e., coordinates of four corners of each of the tail lamps.Further, a maximum luminance value and a minimum luminance value of thepreceding vehicle candidate may respectively take over larger one of themaximum luminance values and larger one of the minimum luminance valuesof the tail lamps. Moreover, an average depth distance of the precedingvehicle candidate may take over shorter one of the average depthdistances of the tail lamps, i.e., may take over larger one of theaverage parallaxes of the tail lamps. The preceding vehicle recognizer172 may also count the number of tail lamps included in the precedingvehicle candidate.

Further, the preceding vehicle recognizer 172 may make a determinationas to whether the presence of the preceding vehicle is confirmed in pastframes at the equivalent three-dimensional positions, and may count thenumber of times that the preceding vehicle is confirmed. The number oftimes that the preceding vehicle is confirmed may influence reliabilityof likelihood that the preceding vehicle candidate is the precedingvehicle. The preceding vehicle recognizer 172 may also make adetermination as to whether the preceding vehicle candidate satisfies acondition that the preceding vehicle candidate has reliability as thepreceding vehicle, and a determination as to whether the precedingvehicle candidate satisfies a condition that the preceding vehiclecandidate lacks the reliability as the preceding vehicle. Moreover, onthe basis of a result of the determination, the preceding vehiclerecognizer 172 may identify the preceding vehicle candidate as thepreceding vehicle, or may remove the preceding vehicle candidate fromthe preceding vehicle candidates. Note that any of various existingtechniques, such as the technique disclosed in JP-A No. 2014-232431, maybe employed for the preceding vehicle recognizing process S210 and adescription of the preceding vehicle recognizing process S210 will notbe given in detail here.

Thereafter, the preceding vehicle recognizer 172 may perform thecorrection of the thus-identified preceding vehicle, on the basis of thetail lamp point and the non tail lamp point both accumulated by thepreceding vehicle extractor 170. Specifically, the preceding vehiclerecognizer 172 may remove the identified preceding vehicle from thepreceding vehicle candidate when the non tail lamp point is equal to orgreater than a predetermined value that may be, for example, 3 (three).The preceding vehicle recognizer 172 may later identify the removedpreceding vehicle as the preceding vehicle again when the tail lamppoint for the removed preceding vehicle is equal to or greater than apredetermined value. In this way, the tail lamp point indicating “thelikelihood that the tail lamp candidate is the tail lamp” is set toreflect more strongly than the non tail lamp point indicating “thelikelihood that the tail lamp candidate is not the tail lamp”. Thecorrection that removes the identified preceding vehicle from thepreceding vehicle candidate may be directed only to the precedingvehicle candidate present in the region determined as being irradiatedwith the high beams. One reason is to stabilize the recognition of thepreceding vehicle.

The predetermined value to be compared with the tail lamp point may varydepending on the number of tail lamps. For example, the predeterminedvalue may be 8 when the number of tail lamps is one, and may be 5 or anyother number when the number of tail lamps is two or more. One reason isto make it difficult to erroneously detect the reflector present aloneon a road shoulder as the tail lamp.

[Oncoming Vehicle Extracting Process S212]

Thereafter, the oncoming vehicle extractor 174 may extract the headlampsfrom the oncoming vehicle detection range 220 b on the basis of aluminance, color information, and a three-dimensional position. Notethat the second luminance image 212 that is based on the short exposuretime may be used due to the headlamps of the oncoming vehicle which aredifferent in light amount from the tail lamps of the preceding vehicleas described above.

Thereafter, the oncoming vehicle extractor 174 may perform grouping ofthe pixels in the oncoming vehicle detection range 220 b. Specifically,the oncoming vehicle extractor 174 may perform the grouping of thepixels in the oncoming vehicle detection range 220 b by collecting thepixels in each of which the luminance is equal to or greater than apredetermined luminance threshold (such as 5 to 10 on a scale from 1 to256) and in which their respective three-dimensional positions arewithin a predetermined distance range (such as falls within 1.5 pixels)with respect to each other. Here, the oncoming vehicle extractor 174 mayperform grouping of the pixels located within a rectangular region. Therectangular region may be defined by horizontal lines and verticallines, and include all of the pixels that satisfy the foregoingconditions. The thus-grouped pixels may be handled as a headlampcandidate that serves as a candidate identifiable as the headlamp. Theheadlamp candidate following the grouping may contain basiccharacteristic amounts such as: coordinates of left, right, top, andbottom parts of the group, i.e., coordinates of four corners of thegroup; the number of pixels in the group; a maximum luminance value inthe group; a minimum luminance value in the group, and an average depthdistance, i.e., an average parallax, of the group.

In the present implementation, the oncoming vehicle extractor 174 mayexclude the grouped pixels from the headlamp candidate when the groupedpixels satisfy any of the following exclusion conditions. For example,the exclusion conditions may include: a difference (a size) between thecoordinates of the left, right, top, and bottom parts of the group whichis equal to or less than a predetermined value (for example, 2 pixels);a difference (a size) between the coordinates of the left, right, top,and bottom parts of the group which is equal to or greater than apredetermined value (which may be determined by the depth distance); andthe number of pixels in the group which is equal to or less than apredetermined value (for example, 2). Note that the predetermined valueto be compared with the luminance may be adjusted by taking intoconsideration the predetermined value in a previous frame. Note that anyof various existing techniques, such as the technique disclosed in JP-ANo. 2014-232430, may be employed for the oncoming vehicle extractingprocess S212 and a description of the oncoming vehicle extractingprocess S212 will not be given in detail here.

The technique according to the preceding vehicle extracting process S208described above may be utilized as it is for the oncoming vehicleextracting process S212. Specifically, the oncoming vehicle extractor174 may recognize that the application range is a region to which thelow beams are to be applied (i.e., the high beams are not to beapplied), when either one of the result information regarding whichapplication range the illumination mechanism 124 has applied the highbeams and the information regarding which application range thelight-distribution controller 184 has instructed the recipient to applythe high beams indicates the application of the low beams application(i.e., when none of them indicates the application of the high beams).For example, the oncoming vehicle extractor 174 may determine that thelow beams are applied when either of those pieces of informationindicates the application of the low beams in a case of the HBA. In acase of the ADB, the oncoming vehicle extractor 174 may determine thatthe low beams are applied when either of those pieces of informationindicates the application of the low beams for any of the angular ranges(i.e., any of the angular regions).

With this configuration, it is possible to continue the detection of theoncoming vehicle in a stable manner by using a low value, i.e., aflexible value, for the threshold. This is possible, for one reason tobe discussed below, even in the situation where the result informationregarding which application range the illumination mechanism 124 hasapplied the high beams still indicates the application of the high beamsdue to the delay in CAN communication or any other factor following thechange of the states of the headlights from the high beams to the lowbeams. One reason is that the information regarding which applicationrange the light-distribution controller 184 has instructed the recipientto apply the high beams indicates the application of the low beams,i.e., does not indicate the application of the high beams. Hence, it ispossible to reduce a possibility that the oncoming vehicle is irradiatedwith the high beams.

Further, the oncoming vehicle extractor 174 may be able to determine, bymeans of calculation, which range in the luminance images 212 the highbeams are applied, on the basis of the angle of view of the block andthe depth distance of the block and the cut-off line angle. With thisconfiguration, it is possible to prevent the occurrence of huntingbetween the high beams and the low beams and thereby reduce thepossibility that the oncoming vehicle is irradiated with the high beams.

[Oncoming Vehicle Recognizing Process S214]

Thereafter, the oncoming vehicle recognizer 176 may perform grouping ofthe headlamps extracted by the oncoming vehicle extractor 174, andrecognize the oncoming vehicle in the oncoming vehicle detection range220 b.

Specifically, the oncoming vehicle recognizer 176 may perform thegrouping of the headlamps and recognize the grouped headlamps as acandidate identifiable as the oncoming vehicle, i.e., an oncomingvehicle candidate, when all of the following conditions are satisfied.For example, the conditions may include: whether a distance in theimages between the headlamps (the groups) falls within a distance rangein which those headlamps are determinable as belonging to the samevehicle, e.g., whether the distance is longer than the predetermineddistance range in the oncoming vehicle extracting process S212; whethera difference in the average depth distance of the headlamps falls withina distance range in which those headlamps are determinable as belongingto the same vehicle; and whether a proportion of the maximum luminancevalue falls within a predetermined range.

The thus-grouped oncoming vehicle candidate may take over the basiccharacteristic amounts of the headlamps before the grouping. Forexample, coordinates of left, right, top, and bottom parts of theoncoming vehicle candidate, i.e., coordinates of four corners of theoncoming vehicle candidate, may take over coordinates that areequivalent to those located outward of the oncoming vehicle candidateamong coordinates of left, right, top, and bottom parts of each of theheadlamps, i.e., coordinates of four corners of each of the headlamps.Further, a maximum luminance value and a minimum luminance value of theoncoming vehicle candidate may respectively take over larger one of themaximum luminance values and larger one of the minimum luminance valuesof the headlamps. Moreover, an average depth distance (an averageparallax) of the oncoming vehicle candidate may take over shorter one ofthe average depth distances of the headlamps, i.e., may take over largerone of the average parallaxes of the headlamps. The oncoming vehiclerecognizer 176 may also count the number of headlamps included in theoncoming vehicle candidate.

Further, the oncoming vehicle recognizer 176 may make a determination asto whether the presence of the oncoming vehicle is confirmed in pastframes at the equivalent three-dimensional positions, and may count thenumber of times that the oncoming vehicle is confirmed. The number oftimes that the oncoming vehicle is confirmed may influence reliabilityof likelihood that the oncoming vehicle candidate is the oncomingvehicle. The oncoming vehicle recognizer 176 may also make adetermination as to whether the oncoming vehicle candidate satisfies acondition that the oncoming vehicle candidate has reliability as theoncoming vehicle, and a determination as to whether the oncoming vehiclecandidate satisfies a condition that the oncoming vehicle candidatelacks the reliability as the oncoming vehicle. Moreover, on the basis ofa result of the determination, the oncoming vehicle recognizer 176 mayidentify the oncoming vehicle candidate as the oncoming vehicle, or mayremove the oncoming vehicle candidate from the oncoming vehiclecandidates. Note that any of various existing techniques, such as thetechnique disclosed in JP-A No. 2014-231301, may be employed for theoncoming vehicle recognizing process S214 and a description of theoncoming vehicle recognizing process S214 will not be given in detailhere.

[Street Light Extracting Process S216]

Thereafter, the street light extractor 178 may extract the street lightsfrom the street light detection range 220 c on the basis of a luminance,color information, and a three-dimensional position, by means of aprocess similar to the process performed in the oncoming vehicleextracting process S212.

[Street Light Recognizing Process S218]

The street light recognizer 180 may recognize the street lightsextracted by the street light extractor 178. Note that the street lightsare not the three-dimensional objects in which the application of thehigh beams is undesirable; however, the recognized street lights may beutilized in a later traveling scene determining process S220.

[Traveling Scene Determining Process S220]

The traveling scene determiner 182 may make the determination as towhether a traveling scene is a traveling scene in which the applicationof the high beams is possible. For example, the traveling scenedeterminer 182 may determine that the traveling scene is the scene inwhich the high beams are unnecessary when a speed of the own vehicle 1is equal to or less than a predetermined value, such as equal to or lessthan 20 km/h. The traveling scene determiner 182 may also determine thatthe traveling scene is the scene in which the high beams are unnecessarywhen the own vehicle 1 makes a left turn or a right turn. The travelingscene determiner 182 may determine that an environment outside the ownvehicle 1 is sufficiently light and thus determine that the travelingscene is the scene in which the high beams are unnecessary when thenumber of street lights present is equal to or greater than apredetermined number, such as 3. Note that any of various existingtechniques, such as the techniques disclosed in JP-A Nos. 2014-232408and 2014-232409, may be employed for the traveling scene determiningprocess S220 and a description of the traveling scene determiningprocess S220 will not be given in detail here.

[Light-Distribution Controlling Process S222]

The light-distribution controller 184 may finally execute thelight-distribution control of the headlamps of the own vehicle 1, on thebasis of the preceding vehicle, the oncoming vehicle, and the travelingscene.

FIG. 14 describes an operation to be performed by the light-distributioncontroller 184. Referring to FIG. 14, when the traveling scenedeterminer 182 determines that the traveling scene is the scene in whichthe high beams are unnecessary, the light-distribution controller 184may refrain from performing the application of the high beams regardlessof whether the light-distribution control is based on the HBA or the ADBand regardless of the number of three-dimensional objects in which theapplication of the high beams is undesirable (such as the precedingvehicle and the oncoming vehicle). For the HBA, when the traveling scenedeterminer 182 determines that the traveling scene is the scene in whichthe use of the high beams is allowed, the light-distribution controller184 may refrain from performing the application of the high beams whenthere is one or more three-dimensional objects in which the applicationof the high beams is undesirable, and may perform the application of thehigh beams when there is no three-dimensional object in which theapplication of the high beams is undesirable. For the ADB, when there isone or more three-dimensional objects in which the application of thehigh beams is undesirable, the light-distribution controller 184 mayperform the application of the high beams on some regions whilepreventing the one or more three-dimensional objects from beingirradiated with the high beams. The light-distribution controller 184may perform the application of the high beams on all of the regions whenthere is no three-dimensional object in which the application of thehigh beams is undesirable for the ADB.

FIG. 15A and FIG. 15B describe the light-distribution control based onthe ADB. When there is one or more three-dimensional objects in whichthe application of the high beams is undesirable in an example where theADB is employed, a maximum width W in a horizontal direction of thethree-dimensional objects as a whole may be calculated to perform theapplication of the high beams on outer side of locations of thethree-dimensional objects as illustrated in FIG. 15A. In an examplewhere it is possible to apply the high beams also to a middle region byapplying the high beams based on the ADB in a divided fashion, a maximumwidth W1 in the horizontal direction of the preceding vehicle and amaximum width W2 in the horizontal direction of the oncoming vehicle, ineach of which the application of the high beams is undesirable, may becalculated to perform the application of the high beams on the middleregion and outer side of locations of the preceding vehicle and theoncoming vehicle as illustrated in FIG. 15B.

Note that, in an example where the ADB is employed, the oncoming vehiclesometimes falls outside the oncoming vehicle detection range 220 b whenthe oncoming vehicle comes extremely close to the own vehicle 1. Toaddress this, the application of the high beams in a direction in whichthe own vehicle 1 and the oncoming vehicle are expected to go by eachother may be halted for a given period of time (such as one second) whenthe oncoming vehicle comes close to the own vehicle 1 by a certain depthdistance (such as 50 meters).

The vehicle exterior environment recognition apparatus 120 according toone implementation is therefore able to perform the light-distributioncontrol of the headlamps appropriately.

In one implementation described above, the central controller 154 mayinclude a semiconductor integrated circuit that may have devices suchas, but not limited to, the central processing unit (CPU), the ROM, andthe RAM. The implementation, however, is not limited thereto. In analternative implementation, the central controller 154 may include anintegrated circuit such as, but not limited to, a field programmablegate array (FPGA) and an application specific integrated circuit (ASIC).The central controller 154 or any other controller may include one ormore central processing units, one or more FPGAs, and/or one or moreASICs.

The implementation also provides a program that causes a computer tofunction as the vehicle exterior environment recognition apparatus 120,and a recording medium that stores the program. The recording medium iscomputer readable. Non-limiting examples of the recording medium mayinclude a flexible disk, a magneto-optical disk, ROM, CD, DVD(Registered Trademark), and BD (Registered Trademark). As used herein,the term “program” may refer to a data processor written in any languageand any description method.

Although some preferred implementations of the technology have beendescribed in the foregoing by way of example with reference to theaccompanying drawings, the technology is by no means limited to theimplementations described above. It should be appreciated thatmodifications and alterations may be made by persons skilled in the artwithout departing from the scope as defined by the appended claims. Thetechnology is intended to include such modifications and alterations inso far as they fall within the scope of the appended claims or theequivalents thereof.

For example, in one implementation described above, the description isgiven by referring to the light-distribution control based on the HBA orthe ADB where appropriate. The implementation, however, is not limitedthereto. Any and all of the processes described above are applicable toany light-distribution control.

Further, the various thresholds set in one implementation describedabove may be modified on an as-needed basis. The thresholds may be seton the basis of values obtained by experience, experiments, or any otherfactor.

A part or all of the processes in the vehicle exterior environmentrecognition process as disclosed herein does not necessarily have to beprocessed on a time-series basis in the order described in the exampleflowchart. A part or all of the processes in the vehicle exteriorenvironment recognition process may involve parallel processing orprocessing based on subroutine.

According to one implementation, it is therefore possible to increaseidentification accuracy of the tail lamps of the preceding vehicle.

The invention claimed is:
 1. A vehicle exterior environment recognitionapparatus comprising: a controller; and a memory storing instructionsthat, when executed by the controller, cause the controller to functionas: a preceding vehicle extractor that extracts a tail lamp of apreceding vehicle from an image based on determining that luminance ofthe tail lamp meets a first threshold; a preceding vehicle recognizerthat determines whether the image includes the preceding vehicle basedon the extracted tail lamp; a light-distribution controller that:determines a light distribution instruction, the light distributioninstruction including one of 1) a first instruction for setting a stateof a headlamp of an own vehicle to a low beam based on determining thatthe image includes the preceding vehicle, and 2) a second instructionfor setting the state of the headlamp to a high beam based ondetermining that the image does not include the preceding vehicle;transmits the determined light distribution instruction to the precedingvehicle extractor and to an illumination mechanism; and the illuminationmechanism that: receives the determined light distribution instructionfrom the light distribution controller; sets the state of the headlampbased on the light distribution instruction, wherein the precedingvehicle extractor: receives, from the light-distribution controller, thedetermined light distribution instruction; receives from theillumination mechanism at a time of receiving the determined lightdistribution instruction, a currently set state of the headlamp;determines that at least one of 1) the determined light distributioninstruction indicating setting the headlamp to the low beam and 2) thecurrently set state of the headlamp indicates the low beam; and adjuststhe first threshold for extracting the tail lamp to a second thresholdthat corresponds to setting the headlamp to the low beam based ondetermining that at least one of 1) the light distribution instructionand 2) the currently set state of the headlamp indicates setting theheadlamp to the low beam.
 2. The vehicle exterior environmentrecognition apparatus according to claim 1, wherein thelight-distribution controller determines, within the image, a region toapply the high beam to, and wherein the light distribution instructionand the set state of the headlamp each contain information on the regionto which the high beam is to be applied.
 3. The vehicle exteriorenvironment recognition apparatus according to claim 2, wherein thepreceding vehicle extractor extracts the tail lamp from an region of theimage based on an angle of view of the image and a depth distance of thetail lamp in the image, and wherein the preceding vehicle extractordetermines whether either one of the light distribution instruction andthe set state of the headlamp indicates the application of the low beamfor the region based on the angle of view in the image and the depthdistance in the image.
 4. The vehicle exterior environment recognitionapparatus according to claim 1, wherein the preceding vehicle extractorextracts the tail lamp from an region of the image based on an angle ofview of the image and a depth distance of the tail lamp in the image,and wherein the preceding vehicle extractor determines whether eitherone of the light distribution instruction and the set state of theheadlamp indicates the application of the low beam for the region basedon the angle of view in the image and the depth distance in the image.